Ambient light sensors are widely utilized in portable electronic devices such as mobile phones, personal data assistants (“PDAs”) and portable computers to sense the intensity of the ambient natural light. Because portable electronic devices are often battery-powered, minimizing power consumption and thereby maximizing device operating time on a single battery charge is an important issue. By sensing the intensity of ambient natural light in the environment where a portable electronic device is being used, information concerning the intensity of ambient natural light can be used to control the amount or degree of backlighting that is provided to a backlit display in the portable electronic device. For example, if the ambient light intensity is high, increased backlighting may be required for a user to view the display. If the ambient light intensity is low, decreased or no backlighting may be required for a user to view the display. Thus, accurately and reliably sensing the intensity of ambient light in portable electronic devices has assumed ever-increasing importance in the bid to prolong portable electronic device single-battery-charge operating times.
Examples of some prior art ambient light sensors include the AVAGO TECHNOLOGIES™ APDS-9002 Miniature Surface Mount Ambient light Photo Diode, the APDS-9003 Miniature Surface Mount Ambient light Photo Diode, the APDS-9004 Miniature Surface Mount Ambient light Photo Diode, the APDS-9005 Miniature Surface Mount Ambient light Photo Diode, the APDS-9006 Miniature Surface Mount Ambient light Photo Diode, the APDS-9007 Ambient Light Photo Sensor with Logarithmic Current, the APDS-9008 Miniature Surface Mount Ambient light Photo Diode, and the APDS-9300 Miniature Ambient Light Photo Sensor with Digital (I2C) Output. A high performance light sensor manufactured by AVAGO TECHNOLOGIES™ is the APDS-9300 sensor, which converts sensed light intensity to a digital signal output capable of direct 12C interface. Each device consists of one broadband photodiode (visible plus infrared) and one infrared photodiode. Two integrating ADCs convert the photodiode currents to a digital output that represents the irradiance measured on each channel. This digital out-put can be input to a microprocessor where illuminance (ambient light level) in lux is derived using an empirical formula to approximate the human-eye response. See, for example, a Data sheet describing the AVAGO TECHNOLOGIES™ APDS-9300 Miniature Ambient Light Photo Sensor with Digital (I2C) Output, hereby incorporated by reference herein in its entirety.
Unfortunately, reliable, accurate and low-cost sensing of ambient light intensity in portable electronic devices remains an elusive goal. What is needed are improved devices, systems and methods for sensing the intensity of ambient light, even in falling light or low-ambient-light conditions, in portable electronic devices that can nevertheless be manufactured and implemented at low cost.